Final answer:
Oral contraceptives prevent pregnancy primarily by inhibiting the release of FSH and LH, essential for ovulation, and by thickening cervical mucus. Missing pills can disrupt hormonal balance and potentially lead to ovulation, making consistent usage critical for effective prevention.
Step-by-step explanation:
Oral contraceptives work by several mechanisms to prevent pregnancy. Primarily, they function by inhibiting the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which are crucial for the ovulation process. Without the release of FSH, follicles do not mature, and without a surge in LH, ovulation does not occur. Additionally, oral contraceptives cause a thickening of the cervical mucus, making it difficult for sperm to reach an egg should ovulation unexpectedly occur.
The continued presence of estrogen and progesterone in birth control pills also feedback onto the hypothalamus and pituitary, reinforcing the inhibition of FSH and LH release. Furthermore, while these hormones do promote some thickening of the endometrial wall, it is insufficient to support implantation, serving as an additional protective measure against pregnancy. It is critical for individuals taking birth control pills to follow the directions consistently, as missing doses can disrupt the hormonal balance and lead to ovulation and potential pregnancy.